The laptop cannot SEE any wireless signals. So it's not MAC address filtering, or WEP/WPA, or anything like that. Those things may prevent him from connecting, but not from SEEING a signal.

Sounds like a flakey laptop to me, assuming the WiFi switch is "on" and so is the router. You might try rebooting the router also. I've seen some go brain-dead and stop with the WiFi part. However, the laptop IS running Windows, and I don't find Windows all that reliable (a separate discussion topic).

For additional troubleshooting, I'd boot the laptop with a Linux LiveCD. If you can get it to detect wireless signal under Linux, then you need to look closer at OS/driver issues when trying with Windows. I would try a Ubuntu LiveCD first, as this distro is more aimed at less experienced/less knowledgable users and thus tends to have better automatic hardware detection (but not always). Knoppix or SystemRescueCD would be good to try also. I haven't used Knoppix for quite a while, but it USED to have decent hardware detection ... I don't know how it stacks up these days however. I've had very good luck recently for many different hardware configurations using SystemRescueCD (based on Gentoo).